Informatics Practices · Ch 5 — Internet and Web
Network Devices
Network Devices
A network is only as useful as the devices that connect it. Without the right hardware, data cannot travel from one computer to another, nor can it cross from one network to a different one. The textbook introduces seven essential network devices, in this order: Modem, Ethernet Card, Repeater, Hub, Switch, Router, and Gateway. Each serves a distinct purpose, and understanding the difference between them is the foundation of networking.
Modem (Modulator-Demodulator)
A modem converts digital signals from a computer into analogue signals that can travel over telephone lines (modulation), and then converts incoming analogue signals back into digital form (demodulation). This device is essential for connecting a home or small office to the internet via a traditional telephone line, cable, or DSL. Without a modem, a computer cannot communicate over the public switched telephone network.
Hub
A hub is a simple, low-cost device that connects multiple computers in a star topology. When a data packet arrives at one port, the hub broadcasts it to all other ports, regardless of which computer the data is actually meant for. This means every connected device receives the traffic, which wastes bandwidth and creates security risks. Hubs operate at the physical layer of the network and do not perform any intelligent filtering.
Switch
A switch looks similar to a hub but works far more intelligently. It learns the MAC addresses of devices connected to each port and forwards data only to the specific port where the destination device is located. This reduces unnecessary traffic and improves network performance. Switches operate at the data link layer and are the standard device used in modern local area networks (LANs) instead of hubs.
Repeater
A repeater is used to extend the physical reach of a network. Signals weaken as they travel over long distances (a problem called attenuation). A repeater receives a weakened signal, regenerates it to its original strength, and retransmits it. It does not filter or interpret the data — it simply boosts the signal so it can travel further without corruption.
Router
A router is the device that connects two or more different networks — for example, connecting a home LAN to the internet. It examines the destination IP address of each data packet and decides the best path for it to reach its destination. Routers operate at the network layer and are the backbone of the internet. They can also perform network address translation (NAT) and act as a firewall.
Gateway
A gateway is the most powerful network device. It connects two networks that use completely different protocols — for example, a LAN using TCP/IP and a mainframe network using SNA. A gateway translates between these protocols so that data can flow seamlessly from one system to another. In practice, a gateway is often a combination of hardware and software, and it can perform the functions of a router, a firewall, and a protocol translator all in one.
In many home networks, the device you call a "router" is actually a combination device: it contains a router, a switch (for wired ports), a wireless access point, and often a modem. The textbook treats each device separately, but real-world hardware frequently combines multiple functions.
Quick Comparison
| Device | Layer | Main Function |
|---|---|---|
| Modem | Physical | Converts digital ↔ analogue signals |